The precise mechanism(s) responsible for follicle rupture and ovum expulsion at the time of ovulation needs to be clarified. Ovarian smooth muscle contractions and local ovarian prostaglandins appear to be associated with the ovulator process. Ovarian contractility increases during the periovulatory interval in the rabbit and appears to be related to the local hormonal milieu within the ovary in monkey and human. Administration of prostaglandin synthesis inhibitors (eg. indomethacin) is associated with inhibition of ovulation without alterations in steroidogenesis in the rabbit, rat and monkey. The proposed investigation is aimed at clarifying the role of ovarian smooth muscle and prostaglandins in the process of mammalian ovulation. The approaches used will include: (1) chronic recordings of ovarian contractility in ovulatory cycles in the rhesus monkey, using intraovarian transducers; (2) studies of ovulation in the in vitro perfused rabbit ovary under various conditions; (3) determination of the effects of indomethacin on spontaneous ovulation in the rhesus monkey; and (4) immunologic and histochemical localization of ovarian smooth muscle and prostaglandin F. In addition to providing basic information regarding the mechanism of ovulation and the requirements essential for follicle rupture, these studies have the potential of ultimately leading to the development of new approaches applicable to regulation of ovulation in the human.